[HELP] Not sure where to post this but this seems like a good start - Linear encoder repair

[Vinny]

Both the black things (both legs) and the clear things (both leads) and check them 2700 things too. You can just leave the black probe connected to ground, but you may also want to measure across the clear and black things. Across the clear and black things if there's a voltage drop it'll tell us if they're good or not.

[Dan Boy]

OK, ill do that in the morning. Thanks.

[EdK]

Those black ones with the stripe are either diodes or capacitors. My guess is capacitors since they would be awfully large wattage diodes for circuitry that runs on such low DC voltage. Ron is probably correct about the "fish eye" parts being photo transistors or diodes.

I would give the printed circuit boards a good scrubbing with some alcohol from the paint department and try seeing if that fixes your problem. You could also use rubbing alcohol but try to get some that doesn't have oil in it.

Ed

[Hopefuldave]

Hi Dan, how's the blower coming along?

In the first photo, it looks like a corroded solder joint on the +5volts powering the infra-red LEDs - between the two Phirrips screw heads are two solder pads, one on the left is probably the 0 volts, one on the right the 5-volt - if you trace the track from that solder pad it goes to the three black-with-stripe diodes and through the to the LEDs - if that joint's bad, the LEDs won't light (invisibly!) to illuminate  the photo-diodes or photo-transistors that switch the outputs on and off. With the reader powered you should see 5v across those pads, and from the 0v to the common ends of the diodes, slightly lower voltage at the far (stripy) end of the diodes.

Try wiggling the wire coming in on the other side of the board while looking at those solder pads through a magnifier (or better a loupe eyeglass) to see whether the joint's still intact, if not first step would be to clean (isopropyl alcohol and a gentle scrape) the pads and wire ends, dab on some flux (Maplin do a "flux pen", a felt-tip with soldering flux in it) and attempt to resolder the wire to the pad.

USE PROPER LEADED SOLDER and a hot iron to minimise the time it takes, or you could cook something, leaded solder's still available for repair work (and military, aviation and medical electronics plus "safety critical" applications, as lead-free isn't as reliable...) although you may not be able to find it in Maplin etc - try EvilBay?

Hope that helps

[oldgoaly]

I'm gonna say your not going to be able to read some of your values on some components in the circuit, a series only circuit you should but series/parallel  you won't. I'm more comfortable with old tube radios. But with a schematic & a few phone a friend radio engineers.... I get by.  it don't help being slightly color blind!  

[Ron Chandler]

Two things that might help in your tests:

1. Photodiodes and phototransistors are "turned on" by exposure to light, so the ohmmeter readings you get are affected by ambient light, so shielding, or shadowing the devices can change the reading that you see.

2. If you want to "see" infrared, take your old video camera, remove the lens and lift out the IR filter in front of the sensor. Replace the lens, look at your IR led's while your device is powered, and you should see a glow if they are live. I haven't tried looking at things with a phone camera, but that might work as well.

[Dan Boy]

OK, thanks for the input. I will try the camera thing mentioned above. I did a test of all components with it plugged into the display screen and the readings were just the same.

Where do I go from here?

[EdK]

(06-21-2015, 12:10 PM)Dan Boy Wrote: OK, thanks for the input.  I will try the camera thing mentioned above.  I did a test of all components with it plugged into the display screen and the readings were just the same.

Where do I go from here?

Did you scrub the boards off as I suggested?

Ed

[Dan Boy]

Hi Ed, I haven't tried that yet as I need to get some degreaser.

Thanks Daniel.

[EdK]

Be careful what you use to clean the boards off. You could do more damage than good.

Ed